As depicted in FIG. 1, a prior art substrate support 100 includes a conventional vertical lift pin 102 that relies on a bushing 106 or collar mounted in a susceptor 104 to provide horizontal support near the top of the lift pin 102 to maintain the pin 102 in a vertical position and limit the angle that the pin 102 can vary from a vertical orientation. An intentionally low friction ceramic skid plate 110 is provided to contact the rounded bottom of the conventional lift pin 102. The conventional lift pin 102 itself typically has a smooth radius bearing surface 108 for contacting the skid plate 110. The ceramic skid plate 110 is mounted on an aluminum plug 112 that is inserted into an opening in the bottom wall 114 of a process chamber. The plug 112 includes an O-ring 116 to maintain the seal of the chamber. Thus, the bushing 106 provides the only horizontal force on the lift pin 102 to guide it as the pin 102 is raised or lowered. The lower end of the lift pin 102 is free to slip on the skid plate 110.
In operation, the susceptor 104 is lowered toward the bottom wall 114 of the chamber which causes the lower bearing surface 108 of multiple lift pins 102 to contact multiple skid plates 110. As the susceptor 104 is further lowered the lift pins rise relative to the susceptor 104 and lift the substrate (not pictured) off of the susceptor 104. Once the substrate has been lifted, a substrate blade (not pictured) such as an end effector may be inserted below the substrate to remove the substrate from the chamber.
In conventional substrate supports, as the bushing 106 wears from guiding the lift pin 102, play may develop in the horizontal position of the lift pin 102 and the bushing's ability to maintain a precise vertical orientation of the lift pin 102 may become compromised. In addition, the lift pin 102 may not travel smoothly through a worn bushing 106 which may affect substrate positioning. Further, the more surface area of a bushing that contacts a lift pin, the more likely it is that potentially contaminating particles may be generated.
An additional problem with conventional lift pins 102 is that they have a tendency to bind in the bushings 106 due to friction such that some lift pins 102 may remain raised above the top surface of the susceptor 104 even as the susceptor 104 is raised. This results in the substrate being lifted unevenly and, in some circumstances, the substrate may be damaged either by a bound lift pin 102 piercing the substrate or suddenly becoming unbound and dropping the substrate. Thus, what is needed is substrate lifting methods and apparatus that are not subject to such problems.